Thermal Hydrolysis of the Lipid and Protein fractions of Wastewater Sludge: Implications for Digester Performance and Operational Considerations
Abstract:Thermal hydrolytic pretreatment of wastewater sludge followed by mesophilic anaerobic digestion poses significant benefits in terms of sludge minimization and pathogen reduction; however, high levels of volatile fatty acids (VFA) in digester effluent reveal an interruption in the efficient conversion of organic material to methane gas. Residual soluble chemical oxygen demand (COD) not only requires additional liquid side wastewater treatment, but also represents lost potential energy recovery in terms of methane gas. High residual VFA concentrations within the digester are attributable to increased VFA loading as a result of thermal hydrolysis of lipids, or from poor fatty acid metabolism due to inhibition. A laboratory study was performed in order to determine the role that thermal hydrolysis temperature plays on the destruction of protein and lipids as well as the production of ammonia and VFA. VFA production was found to more sensitive to hydrolysis temperature between 150°C and 170°C. VFA and ammonia production during thermal hydrolysis both increased as temperature increased from 130°C to 220°C.
This research showed that solids loading rather than hydrolysis temperature would serve as a more meaningful control against high ammonia concentrations within the anaerobic digester. Additionally, it was found that polyunsaturated fats were more amenable to thermal hydrolysis than monounsaturated or saturated fats. This finding has practical implications for sludges rich in lipid type material (i.e. primary sludges) as well as coupled processes of thermal hydrolysis and codigestion of fats, oils, and grease.
Document Type: Research Article
Publication date: 2009-01-01
More about this publication?
- Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed. A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.
WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
- Subscribe to this Title
- Membership Information
- About WEF Proceedings
- WEFTEC Conference Information
- Learn about the many other WEF member benefits and join today
- Ingenta Connect is not responsible for the content or availability of external websites